Molecular genetics of gastric adenocarcinoma in clinical practice

The molecular genetics of gastric carcinoma (GC) dictates their biology and clinical behavior. The two morphologically distinct types of gastric carcinoma by Lauren classification, i.e., intestinal and diffuse cell types, have a significant difference in clinical outcome. These two types of GC have different molecular pathogenetic pathways with unique genetic alterations. In addition to environmental and other etiologies, intestinal type GC is associated with Helicobacter pylori (H. pylori) infection and involves a multistep molecular pathway driving the normal epithelium to intestinal metaplasia, dysplasia, and malignant transformation by chromosomal and/or microsatellite instability (MSI), mutation of tumor suppressor genes, and loss of heterozygosity among others. Diffuse type shows no clear causal relationship with H. pylori infection, but is commonly associated with deficiency of cell-cell adhesion due to mutation of the E-cadherin gene (CDH1), and a manifestation of the hereditary gastric cancer syndrome. Thus, detection of CDH1 mutation or loss of expression of E-cadherin may aid in early diagnosis or screening of diffuse type GC. Detection of certain genetic markers, for example, MSI and matrix metalloproteinases, may provide prognostic information, particularly for intestinal type. The common genetic alterations may offer therapeutic targets for treatment of GC. Polymorphisms in Thymidylate synthase to metabolize 5-fluorouracil, glutathione S-transferase for degradation of Cisplatin, and amplification/overexpression of human epidermal growth factor receptor 2 targeted by monoclonal antibody Trastuzumab, are a few examples. P13K/Akt/mTOR pathway, c-Met pathways, epidermal growth factor receptor, insulin-like growth factor receptor, vascular endothelial growth factor receptor fibroblast growth factor receptor, and micro RNAs are several potential therapeutic biomarkers for GC under investigation.

Earlier onset and multiple primaries in familial as opposed to sporadic esophageal cancer

AIM: To study the differences in onset age and multiple primary cancers between familial and sporadic esophageal squamous cell carcinoma (ESCC).

METHODS: The differences in onset age and multiple primary cancers were analyzed between ESCC patients with (n = 766) and without (n = 1776) a family history of the cancer. The cases analyzed constituted all consecutive patients who had undergone cure-intent surgery at the Department of Thoracic Surgery of the 4^th Hospital of Hebei Medical University from January 1 1975 to December 31 1989. Because we also originally aimed to examine the difference in survival time, only older subjects with a long follow-up period were selected.

RESULTS: Overall, patients with ESCC and a positive family history of the cancer had a significantly younger age at onset and more multiple primary cancers than those without a positive family history (51.83 ± 8.39 vs 53.49 ± 8.23 years old, P = 0.000; 5.50% vs 1.70%, P = 0.000). Both of these differences were evident in subgroup analyses, however, no correlations were observed. While age at onset differed significantly by family history in males, smokers, and drinkers, the difference in multiple primary cancers by family history was significant in nonsmoking, nondrinking, and younger onset patients. In multivariate analysis, age over 50 years, tobacco smoking, and multiple primary cancers were found to be significant predictors of familial cancer: the corresponding OR (95%CI) and P-value were 0.974 (0.963-0.985) and 0.000; 1.271 (1.053-1.535) and 0.012; and 4.265 (2.535-7.176) and 0.000, respectively.

CONCLUSION: Patients with ESCC and a positive family history of the cancer had a significantly younger onset age and more multiple primary cancers than those without a positive family history. Sub-group analyses indicated that younger onset age may be due to the interaction of genetic predisposition and environmental hazards, and multiple primary cancers may only be due to genetic predisposition.

Structure-function relationship in viral RNA genomes: The case of hepatitis C virus

The acquisition of a storage information system beyond the nucleotide sequence has been a crucial issue for the propagation and dispersion of RNA viruses. This system is composed by highly conserved, complex structural units in the genomic RNA, termed functional RNA domains. These elements interact with other regions of the viral genome and/or proteins to direct viral translation, replication and encapsidation. The genomic RNA of the hepatitis C virus (HCV) is a good model for investigating about conserved structural units. It contains functional domains, defined by highly conserved structural RNA motifs, mostly located in the 5’-untranslatable regions (5’UTRs) and 3’UTR, but also occupying long stretches of the coding sequence. Viral translation initiation is mediated by an internal ribosome entry site located at the 5’ terminus of the viral genome and regulated by distal functional RNA domains placed at the 3’ end. Subsequent RNA replication strongly depends on the 3’UTR folding and is also influenced by the 5’ end of the HCV RNA. Further increase in the genome copy number unleashes the formation of homodimers by direct interaction of two genomic RNA molecules, which are finally packed and released to the extracellular medium. All these processes, as well as transitions between them, are controlled by structural RNA elements that establish a complex, direct and long-distance RNA-RNA interaction network. This review summarizes current knowledge about functional RNA domains within the HCV RNA genome and provides an overview of the control exerted by direct, long-range RNA-RNA contacts for the execution of the viral cycle.

Acquisition and dissemination mechanisms of CTXΦ in Vibrio cholerae: New paradigm for dif residents

Vibrio cholerae (V. cholerae) genome is equipped with a number of integrative mobile genetic element (IMGE) like prophages, plasmids, transposons or genomic islands, which provides fitness factors that help the pathogen to survive in changing environmental conditions. Metagenomic analyses of clinical and environmental V. cholerae isolates revealed that dimer resolution sites (dif) harbor several structurally and functionally distinct IMGEs. All IMGEs present in the dif region exploit chromosomally encoded tyrosine recombinases, XerC and XerD, for integration. Integration takes place due to site-specific recombination between two specific DNA sequences; chromosomal sequence is called attB and IMGEs sequence is called attP. Different IMGEs present in the attP region have different attP structure but all of them are recognized by XerC and XerD enzymes and mediate either reversible or irreversible integration. Cholera toxin phage (CTXΦ), a lysogenic filamentous phage carrying the cholera toxin genes ctxAB, deserves special attention because it provides V. cholerae the crucial toxin and is always present in the dif region of all epidemic cholera isolates. Therefore, understanding the mechanisms of integration and dissemination of CTXΦ, genetic and ecological factors which support CTXΦ integration as well as production of virion from chromosomally integrated phage genome and interactions of CTXΦ with other genetic elements present in the genomes of V. cholerae is important for learning more about the biology of cholera pathogen.

Molecular epidemiology of hepatitis B virus in Asia

Although safe and effective vaccines against hepatitis B virus (HBV) have been available for three decades, HBV infection remains the leading cause of chronic hepatitis, cirrhosis and hepatocellular carcinoma (HCC) worldwide, especially in Asian countries. HBV has been classified into at least 9 genotypes according to the molecular evolutionary analysis of the genomic DNA sequence and shown to have a distinct geographical distribution. Novel HBV genotypes/subgenotypes have been reported, especially from Southeast Asian countries. The clinical characteristics and therapeutic effectiveness of interferon (IFN) and nucleos(t)ide analogues vary among different HBV genotypes. Mutations at T1653C in subgenotype C2 from Japan and South Korea, C/A1753T and C1858T in subgenotype C1 from Vietnam, and C1638T and T1753V in subgenotype B3 from Indonesia were reported to be associated with advanced liver diseases including HCC. Genotype distribution in Japan has been changed by an increasing ratio of subgenotype A2 in chronic hepatitis B. While a large number of epidemiological and clinical studies have been reported from Asian countries, most of the studies were conducted in developed countries such as Taiwan, China, South Korea and Japan. In this review, the most recent publications on the geographical distribution of genetic variants of HBV and related issues such as disease progression and therapy in Asia are updated and summarized.

Osteopathia striata with cranial sclerosis, Wilms’ tumor and the WTX gene

Osteopathia striata with cranial sclerosis (OSCS, OMIM#300373) is an X-linked dominant sclerosing bone dysplasia that shows a distinct phenotype in females and males. In 2009, Zandra Jenkins et al found that germline mutations in the FAM123B/WTX/AMER1 gene, mapped to chromosome Xq11.2, cause both the familial and sporadic forms of OSCS. Intriguingly, the WTX gene was already known as a putative tumor suppressor gene, since in 2007 Rivera et al had reported inactivating WTX mutations in Wilms’ tumor (WT), the most frequent renal tumor of childhood. Here we review the heterogeneous clinical presentation of OSCS patients and the involvement of WTX anomalies in OSCS and in WT.

Genetic counseling in post-genomic era: Don’t pretend to know the meaning of a gene mutation if you don’t know

In this post-genomic era, more and more susceptibility loci of many possible genetic diseases are published. As our knowledge about these susceptibility loci is limited and partial, we should be very careful and responsible when patients seek genetic counseling about these possible genetic diseases. We should apply Confucius’s principle about knowledge and information to genetic conseling, and tell the truth to our patients about what we know and what we do not know. Like many other cancers, breast cancer is a very complicated, multifactorial disease; genetic factors, lifestyles and eating habits, environmental factors, and viral infections might be involved in breast cancer; hence, it is difficult to figure out the real etiology of breast cancer. It is not crystal clear that a person who carries mutations of the breast cancer 1, early onset and/or breast cancer 2, early onset genes would eventually get breast cancer in her/his lifetime. No person should undergo a preventive double mastectomy, unless we know the etiology of breast cancer someday.

Regulation of the cell fate by DNA damage and hypoxia

In order to provide the means for the design of novel rational anti-cancer drug therapies research efforts are concentrated on unravelling the molecular circuits which induce programmed cell death and block proliferation of cancer cells. Modern therapeutic strategies are based on the understanding of the complexity of physiological functions such as differentiation, development, immune responses, cell-cycle arrest, DNA damage repair, apoptosis, autophagy, energy metabolism, and senescence. It has become evident that this knowledge will provide the means to target the components of the pathways involved in these processes in a specific and selective manner thus paving the way for the development of effective and personalised anti-cancer therapies. Transcription is a crucial cellular process that regulates a multitude of physiological functions, which are essential in disease progression and cellular response to therapy. Transcription factors such as the p53 tumor suppressor and the hypoxia-inducible factor-α (HIF-α) are key players in carcinogenesis and cellular response to cancer therapies. Both of these transcription factors regulate gene expression of genes involved in cell death and proliferation, in some cases cooperating towards producing the same outcome and in some others mediating opposing effects. It is thus apparent that fine tuning of the activity of these transcription factors is essential to determine the cellular response to therapeutic regimens, in other words whether tumor cells will commit to apoptosis or evade engagement with the anti-proliferative effects of drugs leading to drug resistance. Our observations support the notion that the functional crosstalk between HIF-1α and p53 pathways and thus the fine tuning of their transcriptional activity is mediated by cofactors shared between the two transcription factors such as components of the p300 co-activator multiprotein complex. In particular, there is evidence to suggest that differential composition of the co-modulatory protein complexes associated with p53 and HIF-1α under diverse types of stress conditions differentially regulate the expression of distinct subsets of p53 and HIF-1α target genes involved in processes such as cell cycle arrest, apoptosis, chronic inflammation, and cellular energy metabolism thereby determining the cellular fate under particular types of micro-environmental stress.

An inhibitor of HIF-α subunit expression suppresses hypoxia-induced dedifferentiation of human NSCLC into cancer stem cell-like cells

AIM: To investigate whether hypoxia induces dedifferentiation of non-small cell lung cancer (NSCLC) cells and whether a hypoxia-inducible factor (HIF) inhibitor is able to suppress the process.

METHODS: Human lung adenocarcinoma A549 cells and squamous carcinoma QG56 cells were cultured under normoxic (21% O₂) or hypoxic (4% or 1% O₂) conditions. The expression of the following genes were examined by reverse transcription-polymerase chain reaction, Western blotting and/or immunofluorescence: HIF-1α and HIF-2α subunits; differentiation marker genes, namely surfactant protein C (SP-C) (type II alveolar cell marker), CC10 (type I alveolar cell marker) and aquaporin 5 (AQP5) (Clara cell marker); and stem cell-associated genes, namely CD133, OCT4, and Musashi-1 (MSI1). The tumor sphere-forming ability of the cells was evaluated by culturing them in serum-free growth factor-rich medium containing epidermal growth factor (EGF) and fibroblast growth factor (FGF). CD133 expression in hypoxic regions in A549 tumors was examined by double-immunostaining of tissue cryosections with an anti-2-nitroimidazole EF5 antibody and an anti-CD133 antibody. The metastatic ability of A549 cells was examined macroscopically and histologically after injecting them into the tail vein of immunocompromised mice.

RESULTS: A549 cells primarily expressed SP-C, and QG56 cells expressed CC10 and AQP5. Exposure of A549 cells to hypoxia resulted in a marked down-regulation of SP-C and upregulation of CD133, OCT4, and MSI1 in a time-dependent manner. Moreover, hypoxia mimetics, namely desferrioxamine and cobalt chloride, elicited similar effects. Ectopic expression of the constitutively active HIF-1α subunit also caused the downregulation of SP-C and upregulation of CD133 and MSI1 but not OCT4, which is a direct target of HIF-2. Hypoxia enhanced the sphere-forming activity of A549 cells in serum-free medium containing EGF and FGF. Similarly, hypoxia downregulated the expression of CC10 and AQP5 genes and upregulated CD133, OCT4, and MSI1 genes in QG56 cells. TX-402 (3-amino-2-quinoxalinecarbonitrile 1, 4-dioxide), which is a small molecule inhibitor of the expression of HIF-1α and HIF-2α subunits under hypoxic conditions, inhibited the upregulation of SP-C and hypoxia-induced down-regulation of CD133, OCT4, and MSI1. Notably, TX-402 significantly suppressed the hypoxia-enhanced lung-colonizing ability of A549 cells.

CONCLUSION: Hypoxia induces the de-differentiation of NSCLC cells into cancer stem cell-like cells, and HIF inhibitors are promising agents to prevent this process.

Genomic microarrays in prenatal diagnosis

The application of microarray-based techniques for the diagnosis of genomic rearrangements has been steadily growing in popularity since its introduction in 2004. Given the many advantages of these techniques over conventional cytogenetics, there is increasing pressure towards their application in prenatal diagnosis. However, there remain several important issues that must be addressed. For example, microarray-based techniques (comparative genomic hybridization-based arrays and single nucleotide polymorphism-based arrays) allow detection of even very small genomic imbalances that can determine pathological clinical conditions. In addition, there are other copy number variations which represent normal variation, with no detectable effects on phenotype. Given the still incomplete knowledge of the changes in our genome and the associated phenotypes, microarray-based diagnosis is likely to find variants of uncertain and unknown clinical significance. The interpretation of these variants is now a major challenge for the medical geneticist, who often find it difficult to establish precise correlations between genotype and phenotype. There is sufficient available evidence to justify the use of microarray-based diagnostics for a select number of specific conditions, but there is also an inevitable trend towards ever wider application. It is very important that this drift does not progress in an unchecked and uncontrolled manner under the thrust of commercial interests. Therefore, we recommend that scientific societies be vigilant and take an advisory role in the adopting of these technologies as new scientific knowledge becomes available.

Genetic alterations in head and neck squamous cell carcinoma: The next-gen sequencing era

Head and neck squamous cell carcinoma is the sixth most common cancer in the world with approximately 650000 new cases diagnosed annually. Next-generation molecular techniques and results from phase 2 of the Cancer Genome Atlas becoming available have drastically improved our current knowledge on the genetics basis of head and neck squamous cell carcinoma. New insights and new perspectives on the mutational landscape implicated in head and neck squamous cell carcinoma provide improved tools for prognostication. More importantly, depend on the patient’s tumor subtypes and prognosis, deescalated or more aggressive therapy maybe chosen to achieve greater potency while minimizing the toxicity of therapy. This paper aims to review our current knowledge on the genetic mutations and altered molecular pathways in head and neck squamous cell carcinoma. Some of the most common mutations in head and neck squamous cell carcinoma reported by the cancer genome atlas including TP53, NOTCH1, Rb, CDKN2A, Ras, PIK3CA and EGFR are described here. Additionally, the emerging role of epigenetics and the role of human papilloma virus in head and neck squamous cell carcinoma are also discussed in this review. The molecular pathways, clinical applications, actionable molecular targets and potential therapeutic strategies are highlighted and discussed in details.

Genetic counselling in post-genomic era-to be or not to be

With the surge of genetic tests and technologies, genetic counsellors are faced with the challenge of translating emerging scientific knowledge into practical information for patients, clinicians and public health policy makers. The new tests and technologies also are associated with new psychosocial and ethical considerations. New guidelines are needed for each new discovery of the genomic impact on phenotype, pathology and disease while “old” syndromes and “old” pathology, continue to require attention. In the new post-Human Genome Project era, genetic counsellors will be an integral part of translating genomic discoveries into beneficial impact on human disease, health care, and medical benefits. The needs for genetic counselling should be designed into genomic research at the onset. Genetic counsellors need to handle old while rapidly assimilating new information and the principal challenge is to be up to date and updated.

Fiber-fluorescence in situ hybridization analyses as a diagnostic application for orientation of microduplications

Microduplications are normally invisible under microscopy and were not recognized before chromosomal microarray testing was available. Although it is difficult to confirm the orientation of duplicated segments by standard fluorescence in situ hybridization (FISH), our data indicates that fiber-FISH analysis has the potential to reveal the orientation of duplicated and triplicated segments of chromosomes. Recurrent microduplications reciprocal to microdeletions show tandem orientations of the duplicated segments, which is consistent with a non-allelic homologous recombination mechanism. Several random duplications showed tandem configurations and inverted duplications are rare. Further analysis is required to fully elucidate the basic mechanisms underlying such duplications/triplications.

Malignant pheochromocytoma in neurofibromatosis; mutation screening of RET proto-oncogene, VHL and SDH gene

AIM: To investigate pathogenic mutations related to malignant pheochromocytoma in neurofibromatosis (NF).

METHODS: We present a patient with NF and metastatic pheochromocytoma in whom genetic screening for presence of pathogenic mutations in RET proto-oncogene, von Hippel-Lindau (VHL) and succinate dehydrogenase complex subunits B (SDHB) genes were investigated. RET proto-oncogene mutation screening for exons 10, 11, 13, 14, 15, 16 were examined by polymerase chain reaction (PCR) and direct DNA sequencing in patient. Mutation screening for exons 1, 2, 3 of VHL gene was carried out. Both forward and reverse strands were subjected to direct sequencing after PCR amplification. The entire coding sequence of SDHB gene was screened for the presence of pathogenic mutations by PCR-sequencing.

RESULTS: A 45-year-old man presented with abdominal pain and hypertension over the previous year. The patient was a known case of neurofibromatosis type 1 (NF1) who presented at the age of 15 years with hyperpigmented and hypopigmented lesions. After complete evaluation for hypertension, biochemical tests and imagings indicated a malignant pheochromocytoma of 120 mm × 70 mm in size. The patient underwent left adrenalectomy, nephrectomy and splenectomy. After surgery the symptoms improved and blood pressure was controlled. After 5 years he was admitted again for evaluation of hypertensive crisis. Biochemical tests were again consistent with pheochromocytoma and disease relapse. Imaging studies and liver biopsy confirmed metastatic pheochromocytoma to the liver and para-aortic area. 131 Iodine-metaiodobenzylguanidine therapy was carried out. Genetic screening of VHL (exons 1, 2, 3), RET proto-oncogene (exons 10, 11, 13, 14, 15, 16) and SDH complex subunits revealed no pathogenic mutation.

CONCLUSION: We conclude that mutations in the NF1 gene are responsible for the patient’s clinical findings. However, would be helpful to further examine somatic mutations for a more precise study of genotype-phenotype correlation.

Prevalence of fragile X syndrome in males and females in Indonesia

AIM: To investigate the prevalence of fragile X syndrome (FXS) in intellectually disabled male and female Indonesians.

METHODS: This research is an extension of a previously reported study on the identification of chromosomal aberrations in a large cohort of 527 Indonesians with intellectual disability (ID). In this previous study, 87 patients had a chromosomal abnormality, five of whom expressed fragile sites on Xq27.3. Since FXS cannot always be identified by cytogenetic analysis, molecular testing of the fragile X mental retardation 1 CGG repeat was performed in 440 samples. The testing was also conducted in the five previously identified samples to confirm the abnormality. In total, a molecular study was conducted in 445 samples (162 females and 283 males).

RESULTS: In the cohort of Indonesian ID population, the prevalence of FXS is 9/527 (1.7%). The prevalence in males and females is 1.5% (5/329) and 2% (4/198), respectively. Segregation analysis in the families and X-inactivation studies were performed. We performed the first comprehensive genetic survey of a representative sample of male and female ID individuals from institutions and special schools in Indonesia. Our findings show that a comprehensive study of FXS can be performed in a developing country like Indonesia where diagnostic facilities are limited.

CONCLUSION: The prevalence of FXS is equal in females and males in our study, which suggests that the prevalence of FXS in females could be underestimated.

Preimplantation testing: Transition from genetic to genomic diagnosis

Preimplantation genetic testing refers to the procedure to determine the genetic status of embryos formed by in vitro fertilization (IVF) prior to initiating a pregnancy. Traditional genetic methods for preimplantation genetic diagnosis (PGD) examine distinct parts of an individual genome, require the development of a custom assay for every patient family, and are time consuming and inefficient. In the last decade technologies for whole-genome amplification (WGA) from single cells have led to innovative strategies for preimplantation testing. Applications of WGA technology can lead to a universal approach that uses single-nucleotide polymorphisms (SNPs) and mutations across the entire genome for the analysis. Single-cell WGA by multiple displacement amplification has enabled a linkage approach to PGD known as “preimplantation genetic haplotyping”, as well as microarray-based techniques for preimplantation diagnosis. The use of microarrays in preimplantation diagnosis has provided genome-wide testing for gains or losses of single chromosomes (aneuploidies) or chromosomal segments. Properly designed randomized controlled trials are, however, needed to determine whether these new technologies improve IVF outcomes by increasing implantation rates and decreasing miscarriage rates. In genotype analysis of single cells, allele dropout occurs frequently at heterozygous loci. Preimplantation testing of multiple cells biopsied from blastocysts, however, can reduce allele dropout rates and increase the accuracy of genotyping, but it allows less time for PGD. Future development of fast SNP microarrays will enable a universal preimplantation testing for aneuploidies, single-gene disorders and unbalanced translocations within the time frame of an IVF cycle.

Evolving ethical issues in third party reproduction: Local and global considerations

There continues to be an increase in utilization of assisted reproductive technology (ART), including the use of third party gametes. Specifically, the use of third party oocytes, most recently reported in 2010 by the United States (US) Center for Disease Control and Society of Reproductive Medicine, accounted for 15 504 cycles and 7334 live births. This translates into approximately 11% of all the in vitro fertilization cases performed in the US. As utilization increases and the technological tools advance, they have created underappreciated and unforeseen ethical quandaries. As such, many practitioners think they “have heard it all”. However, each ART scenario is novel with the potential to pose complex unforeseen issues, potentially creating global challenges that could impact broad social and legal questions and test the moral consciousness’ of practitioners, policymakers and patients. While there are published US national guidelines to assist practitioners, we have identified new complex issues in assisted reproduction that present unique challenges, and we give a perspective from our eyes in the Western Hemisphere looking out to a global level. Specifically, this review focuses on some of the more recent and evolving issues that currently are and will be confronting us in the upcoming years. Particular attention focuses on discrepancies between third party legal contracts and ART consents regarding level of information sharing, and oocyte and embryo directives and management; dilemmas and obligations surrounding disclosure of medical outcomes especially in the context of growing access to Direct to Consumer genetic testing and Reproductive Tourism-Exile. Given the complexity of these and other ethical questions, finding answers may be achieved by ending the isolation of reproductive professionals and instead promoting increased and consistent communication among physicians, embryologists, therapists and reproductive attorneys to confront these evolving ethical quandaries.

What is the purpose of launching the World Journal of Medical Genetics?

Congratulations to the publisher, members of the editorial board of the journal, all the authors and readers for launching the World Journal of Medical Genetics (WJMG) as a new member of the World series journal family! Following the completion of the Human Genome Project, medical genetic research has seen spectacular progress over the last decade. The number of genes that have been linked to Mendelian human traits has grown exponentially and currently this process is peaking with the access to robust genome-wide sequencing power. The genomics revolution is also seen for elucidation of rare and common DNA variants that increase risk for common disorders. Given this fast progress, there is an increasing need for making the results of genetics and genomics studies rapidly and freely available to the larger community. Thus, the decision for inaugurating this new journal is a timely one. The WJMG is a peer-reviewed, open-access periodical centered in all aspects of medical genetics research, with multidisciplinary coverage: from human phenotype to genetic and genomic mutations and variations to the study of pathological mechanisms. If you want to share new results of your research with a link to medical genetics with your peers, you will find the WJMG a good media to publish your papers!

Genome-wide association studies: Where we are heading?

We have witnessed tremendous success in genome-wide association studies (GWAS) in recent years. Since the identification of variants in the complement factor H gene on the risk of age-related macular degeneration, GWAS have become ubiquitous in genetic studies and have led to the identification of genetic variants that are associated with a variety of complex human diseases and traits. These discoveries have changed our understanding of the biological architecture of common, complex diseases and have also provided new hypotheses to test. New tools, such as next-generation sequencing, will be an important part of the future of genetics research; however, GWAS studies will continue to play an important role in disease gene discovery. Many traits have yet to be explored by GWAS, especially in minority populations, and large collaborative studies are currently being conducted to maximize the return from existing GWAS data. In addition, GWAS technology continues to improve, increasing genomic coverage for major global populations and decreasing the cost of experiments. Although much of the variance attributable to genetic factors for many important traits is still unexplained, GWAS technology has been instrumental in mapping over a thousand genes to hundreds of traits. More discoveries are made each month and the scale, quality and quantity of current work has a steady trend upward. We briefly review the current key trends in GWAS, which can be summarized with three goals: increase power, increase collaborations and increase populations.

Overlap of genetic influences in phenotypes classically categorized as psychiatric vs medical disorders

Psychiatric disorders have traditionally been segregated from medical disorders in terms of drugs, treatment, insurance coverage and training of clinicians. This segregation is consistent with the long-standing observation that there are inherent differences between psychiatric disorders (diseases relating to thoughts, feelings and behavior) and medical disorders (diseases relating to physical processes). However, these differences are growing less distinct as we improve our understanding of the roles of epistasis and pleiotropy in medical genetics. Both psychiatric and medical disorders are predisposed in part by genetic variation, and psychiatric disorders tend to be comorbid with medical disorders. One hypothesis on this interaction posits that certain combinations of genetic variants (epistasis) influence psychiatric disorders due to their impact on the brain, but the associated genes are also expressed in other tissues so the same groups of variants influence medical disorders (pleiotropy). The observation that psychiatric and medical disorders may interact is not novel. Equally, both epistasis and pleiotropy are fundamental concepts in medical genetics. However, we are just beginning to understand how genetic variation can influence both psychiatric and medical disorders. In our recent work, we have discovered gene networks significantly associated with psychiatric and substance use disorders. Invariably, these networks are also significantly associated with medical disorders. Recognizing how genetic variation can influence both psychiatric and medical disorders will help us to understand the etiology of the individual and comorbid disease phenotypes, predict and minimize side effects in drug and other treatments, and help to reduce stigma associated with psychiatric disorders.

Research progress in the cell origin of basal cell carcinoma

Identification of the cell origin of human neoplasms remains a challenging but important task in cancer research. The outcomes in this area of study may allow us to design novel strategies for early cancer detection and targeted cancer therapeutics. Skin is a great organ to study cancer stem cells because stem cells in skin have been well investigated and approaches of genetic manipulation in specific cell compartments are available to mimic clinical skin cancer in a mouse model. Recently, by using different genetic engineered mouse models, several groups have tried to discover which cell type in skin was responsible for the initiation of basal cell carcinoma, the most common type of skin cancer. These studies raised more questions but also showed more ways for future investigation.

Genetic interactions in translational research on cancer

Genetic interactions are functional crosstalk among different genetic loci that lead to phenotypic changes, such as health or viability alterations. A disease or lethal phenotype that results from the combined effects of gene mutations at different loci is termed a synthetic sickness or synthetic lethality, respectively. Studies of genetic interaction have provided insight on the relationships among biochemical processes or pathways. Cancer results from genetic interactions and is a major focus of current studies in genetic interactions. Various basic and translational cancer studies have explored the concept of genetic interactions, including studies of the mechanistic characterization of genes, drug discovery, biomarker identification and the rational design of combination therapies. This review discusses the implications of genetic interactions in the development of personalized cancer therapies, the identification of treatment-responsive genes, the delineation of mechanisms of chemoresistance and the rational design of combined therapeutic strategies to overcome drug resistance.